package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import org.yaml.snakeyaml.events.Event;
import org.yaml.snakeyaml.tokens.Token;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    //自带value的str转json序列化
    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }
    //逻辑过期
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    //缓存穿透
    public <R, ID> R queryWithPassTrough(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback,  Long time, TimeUnit unit){
        String key = keyPrefix + id;
        //1.从redis查询商户缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在-返回
            return JSONUtil.toBean(json, type);
        }
        //判断命中的收否是空值
        if (json != null){
            // 返回一个错误信息
            return null;
        }
        //4.不存在-查询数据库
        R r= dbFallback.apply(id);
        //5.不存在-返回错误
        if (r == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在-写入redis-返回
        this.set(key, r, time, unit);
        //7.返回
        return r;
    }

    //线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool( 10);
    //逻辑过期代码封装
    public <R,ID> R queryWithLogicalExpire(
            String keyRefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit){
        String key = keyRefix + id;
        //1.从redis查询商户缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)) {
            //3.存在-返回
            return null;
        }
        //4.命中，需要判断过期时间，需要把json反序列化
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1 未过期-返回店铺信息
            return r;
        }
        //5.2 已过期-缓存重建
        //6. 缓存重建
        String lockKey = LOCK_SHOP_KEY + id;
        //6.1 获取互斥锁
        Boolean isLock = tryLock(lockKey);
        //6.2 判断是否获取成功
        if (isLock) {
            // 6.3 成功，开启独立线程实现缓存重建(线程池)
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //查数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }

        //6.4 失败返回商铺信息
        return r;
    }
    //获取锁
    private Boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //删除锁
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}
